<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            background-color: red;
            /* 私有前缀 */
            -webkit-transition: all 1s;
        }
        div:hover{
            width: 300px;
            height: 300px;
        }
    </style>
</head>
<body>
<div></div>
</body>
</html>